Milo g



(N0 Mode 1.)

. M. G. KELLOGG.

MULTIPLE SWITGHBOARD.

No. 592,349. Patent ed Oct. 26,1897.

......................... |v v I V UNITED STATES PATENT Curios.

MILO G. KELLOGG, OF CHICAGO, ILLINOIS, ASSIGNOR TO THE KELLOGG SIVITCIIBOARD AND SUPPLY COMPANY, OF SAME PLACE.

M ULTI PLE SWITCHBOARD.

SPECIFICATION forming part of Letters Patent No. 592,349, dated October 26, 1897.

Application filed January 2,1890. Serial No. 335,699. (No model.)

To all whom it may concern:

Be it known that I, MILO G. KELLOGG, of Chicago, in the county of Cook and State of Illinois, temporarily residing at Stuttgart, in the Empire of Germany, have invented certain new and useful Improvements in Multiple Switchboards for Telephone-Exchanges, of which the following is a full, clear concise, and exact description, reference being had to the accompanying drawings, forming a part of this specification.

My invention relates to a telephone-exchange system in which the lines are lines grounded at their outer ends; and it consists of a system of testing the lines to determine whether they are in use.

In the drawings illustrating my invention, Figures 1 and 1 represent sections of two multiple switchboards of the exchange to which the same lines are connected. Fig. 2 shows a diagram of the boards with the main-line apparatus and connections necessary to illustrate my invention. Fig. 2 is a detail View of one of the line-annunciators. Fig. 3 shows a diagram of an operators cord system to be used in connection with the boards. Fig. 4 shows an operators test system to be used at the boards. Fig. 5 shows a subscribersstation apparatus.

G represents in each case a ground connection.

In Fig. 9, A is a sectional view of the switchboard shown in Fig. l, and A is a sectional view of the switchboard shown in Fig. 1", each as indicated by the line (1 e.

I place as many boards in thecentral office as are found necessary or desirable in orderto properly operate the exchange. On'each board is a spring-jack or other suitable switch for each line. Each switch has a contactspring which normally connects with an insulated contactpiece and is adapted to receive a loop-plug and, when a plug-is inserted, to disconnect the spring from the contactpiece and connect the two contact-pieces of the plug with the spring and said insulated contact-pieces, respectively. The switch is also adapted to receive a single contact switch-plug and, when a plug is inserted, to disconnect the spring from the contact-piece and connect the spring with the contact-piece of the plug. In the construction of the switches as shown and as will hereinafter be described I prefer to have a contact-point electrically connected with the contact-piece and on which the spring normally bears, as there is less chance of poor connection when the spring bears on a point than when it bears on a surface adapted to be brought into connection with the plug-contacts.

In Fig. 2, g g represent the springs of the different switches, h h the contact-points on which the springs normally bear, and j j the contact-pieces of the switches connected with the points h h. Z Z are the switchholes. a l) are the rubber strips on which the metal parts of the switches are mounted, as shown, and

through the fronts of which are the switchholes Z Z. The contact-pieces jj are so placed along one of the surfaces of the plug-holes as readily to form connection with one of the contact-pieces of the loop-plugs. The holes Z Z are adapted to receive the switch-plugs shown in Fig. 3 and marked D D, and when a plug is inserted into a switch it raises the spring 9 from the contact-point h, and the spring g and contact-piece of the plug are in contact. These holes are also adapted to receive the loop-plug shown in Fig. 4, and when a plug is inserted into a hole it raises the spring of the switch from the contactpoint h, and the spring 9 and the contactpiece 3' of the switch are in contact with the two contact-pieces of the plug, respectively.

W and X are calling-annunciators, one for each of the lines shown. Each annunciator has a pair of contact-points normally (or when the annunciator does not indicate a call) in contact with each other, but which are separated by the annunciator While it indicates a call. The two contact-points of a pair are marked 19 and g, respectively. One of them, q, is a spring-contact which is pressed by the annunciator-drop, when the drop falls, away from its corresponding contact-pointp. The contact-point p is represented as an anglepiece which passes over the spring (1 and is in contact with the spring when the spring is not actuated by the annunciator-drop.

The annunciator is shown in detail in Fig. 2. The line runs to an insulated bolt 0 at the top of the annunciator-plate 0, thence passing to each spring first. Itthen passes through its line-annunciator and the pair of contact-points of theannunciator to the ground. The circuit of each line shown may thus be traced in Fig. 2.

In the operators cord system shown in Fig. 3, D D are the switch-plugs of a pair of cords. n n are the rubber insulators of the plugs, and m m are their contact-pieces. These contact-pieces pass each to the bottom of its plug and are adapted to rest normally, or when the plug is not in use, on the metal piece 0, which then connects it with .the ground. Weights, as is usual, or similar devices maybe used to bring the contact-pieces of the plugs into contact with the piece 0 and secure a good connection. These plugs are adapted to be inserted into any of the switches at their board, and when a plug is inserted it operates the switch, as above described. The plugs should be inserted so that the contact-piece m is in contact with the spring 9. The connections of the lines might have been reversed, so that the lines pass first to the contact-piece j of each of their switches, and in that case the plugs should be inserted] insuch a position that their contact-pieces form connection with the pieces j of the switches.

cords shown.

K is the calling-key, and Q) is a clearingout-annunciator.

of the pairs of contact-bolts of the switch are connected together through the clearing-out annunciator andthe other pair are connected through the operators telephone. The lever of the calling-key is connected to one of the cords and the point of the key is grounded through the calling generator or battery.

The operation of the system in connection with the switchboards will be apparent to those skilled in the art. It will readily be apparent-that when a line is switched by the insertion of a plug into its switch the line is disconnected from its normal ground at the central office and is connected into a circuit withthe pair of cords. Only one pair of cords the lever. Y is the looping-in switch for the pair of are shown, but the connection of such other pairs with their accompanying apparatus as the operator may need will be apparent to those skilledin the art. To each pair of cords with its plugs belong a looping-in switch, a

clearing-out annunciator, and a calling-key. One telephone and one calling-generator will answer for her system of cords.

In the operators test system shown in Fig. 4, T is a loop test-plug adapted to be inserted into any of the switches and, when inserted,

to operate them, as heretofore described. 13' is a test-battery, and S is a test receiving instrument. The battery and instrument are connected in a loop which terminates in the two contact-pieces of the plug.

Each operator has one cord system and one test system, and they are conveniently mounted and arranged for her work.

In the subscribers-station apparatus shown in Fig. 5, 1 is the telephone-switch. 2 is the calling-generator. 3 is the signal-receiving hell. 4 is the subscribers telephone. 5 is the secondary, and 6 is the primary, of the induction-coil.

7 is the transmitter. Sis the transnutter-battery. 9 is a resistancecoil of suitable resistance to operate, as hereinafter described. These parts may be of usual forms of apparatus and are connected as shown or in other ways so as to perform practically the operations required and theoperations hereinafter described. The line passes through the resistance-coil 9, thence through the telephone and the secondary and primary of the induction-coil to the lever of the switch, and

I thence through the signal-bell and callinga generator to ground. A circuit-wire of small resistance passes from the line between the subscribers station and the resistance-coil to a contact point against which the switchlever is in contact when the telephone is on Another wire of small resistance passes from the circuit between the signalbell and the oftice ground to a contact-point against which the lever comes in contact when freed from the weight of the telephone. A

,. third circuit-wire passes from the connection between the primary and secondary of the induction-coil through the transmitter and battery to a contact-point against which the switch-lever comes in contact when relieved of the weight of the telephone.

When the subscribers telephone is on its switch, the signal-receiving bell is in the circuit of the line, and the telephone, the secondary of the induction-coil, and the resistancecoil are shunted by a wire of small resistance, so as to be practically out of the circuit. When the telephone is off the switch, the telephone, the secondary of the induction-coil, and the resistance-coil are in the circuit and the signal-bell is practically out of the circuit. The resistance of the telephone and secondary of the induction-coil combined aggregate in well-constructed apparatus about four hundred ohmsand the resistance of the signal-bell amounts to about one hundred ohms. The

resistance switched into the circuit when the telephone is off its switch for use is therefore much greater than is the resistance in the circuit when the telephone is in its normal position on the switch. I utilize this difference in resistance in the operation of the test system, as will hereinafter appear. If thedil'ference in the resist-ance when the telephone is oft its switch for use and when it is in its normal position on the switch is not sufficient to secure an easy adjustment of the test apparatus to the circuits, such additional resistance as is required may be placed in the resistance-coil 9. .Vhether this artificial resistance is used and its amount, if used, will depend on the apparatus and circuits to which the system maybe applied. The test receiving instruments and test-batteries are then so adjusted to each other and the circuits that the instrument will sound or respond when it and its battery are looped into the closed cir-\ cuit of any single line and the subscribers telephone is not oit its switch for use, but will not respond if the circuit is open at any point, or if the subscribers telephone is off its switch and the additional resistance at the subscribers station is included in the circuit, or the line is in circuit with another line and thereby additional resistance is in the circuit with the line. This adjustment can be regulated as required by the addition of artificial resistances in the circuits. This construction and adjustment depends on the fact that an electromagnet may be readily made so as to operate when a battery and a certain resistance is in circuit with it andnot to operate when the resistance is considerably larger. This operation can be obtained in different ways dependent on the style of the electromagnet, the number of convolutions of its coil, the size of the battery, and the adjustment of the retractile spring. These parts should be such that the electromagnet will be actuated when the test system is looped into the single circuit of any line of the exchange, but will not be actuated when the additional resistance is introduced. The resistance of the coils may be such as is necessary or desirable in order to obtain such an adjustment of the parts of the exchange system.

The operation of the test system is as follows: When an operator desires to test a line, she places her test-plug into the switch of the line and by so doing disconnects the pointsg and j of the switch and connects them with the contact-pieces of the plug. It, then, the line is not switched at any board and the annunciator does not indicate a call and the subscribers telephone is on its switch, the test receiving instrument will sound or respond, indicating that the line is free to be switched to. If, however, the subscriber has sent in a call and the annunciator indicates the call or has taken his telephone from the switch for use, the instrument will not sound, as the line being open at the annunciatorpoints or the additional resistance in the circuit will prevent it from doing so. If, again, the line is switched at some board and the test is made in the cut-oil? portion of the linethat is, that portion which is between the switch used for switching and the oflice groundthe instrument will not sound because the test-circuit is open at the pair of contact-points of the switch used for switching. If, again, the line is switched at any board with another line, the instrument will not sound on account of the increased resistance of the circuit.

When a test of a line is made and the test receiving instrument sounds, the operator knows that neither the line is switched for use nor the subscribers telephone is switched for use nor the line-annunciator indicates a call, and when the instrument does not sound she knows that either the annunciator indicates a call or the subscribers telephone is switched for use or the line is switched for use, and she will not connect the line with an y other line.

By this system a subscribers line is reserved to himself from the time he sends in his call or takes his telephone down for use.

In this system only two switch-contacts are required for each line on each board instead of three or more, as in other systems with ground-circuit lines, and there are onlytwo leading-in wires to each switch instead of three or more, as in other systems. There is also but one wire required for each line for the connection between her boards instead of two or more, as in other systems.

I claim as my invention and desire to secure by Letters Patent- 1. In a telephone-exchange system, a telephone line normally passing successively through pairs of switch contact-poi11ts, one pair on each of several boards, each pair normally closed, but open while the line is switched at their board and through an annunciator and a pair of contact-points normally closed but open while the annunciator indicates a call, in combination with switching devices at each board to disconnect said pair of contact-points at the board and switch the line for conversation, apparatus and switching devices at the subscribers station to include a greater resistance in the circuit of the'line while the subscribers telephone is switched for use than when it is not thus switched, and a loop test-plu g in the two contact-pieces of which terminate the two sides of a loop containing a test receiving instrument and battery, said plug being adapted to be inserted into one of the switches and when inserted to disconnect its said contact-points which are normally in contact and connect them with the contact-pieces of the plug, said test receivinginstrument being so related and adjusted that it will sound when looped into IIO the simple normal closed circuit of the line switched for use and the additional resistance thereby included in the circuit, substantially as set .forth.

2. In a telephone-exchange system, a telephone-line grounded at its outer end and normally passing successively through pairs of switch contact-points, one pair on each of several boards, each pair normally closed but open while the line is switched at their board and through an annunciator and a pair of contact-points normally closed but open while the annunciator indicates a call, and thence to the ground in combination with switching devices at each board to disconnect said pair of contact-points at the board and switch the line for conversation,

apparatus and switching devices at the subscribers station to include a greater resistance in the circuit of the line while his telephone is switched for use than when it is not thus switched, and a loop test-plug in the two contact-pieces of which terminate the two sides of a test-loop containing a test receiving instrument and battery, said plug being adapted to be inserted into one of the switches and when inserted to disconnect the contact-points of the switch which are normally in contact and connectthem with the two contact-pieces of the plug, said test receiving instrument and battery being so relateda-nd adjusted that the instrument will sound when they are included in the simple normal circuit of the line (the subscribers telephone not being switched for use) but will not sound when included in circuit with the line and the circuit is open or the line is p in circuit with another line or the telephone is switched for use and the additional resistance thereby included in the circuit, substantially as set forth.

3. In a telephone-exchange system, a telephone-line normally on closed circuit and passing successively through pairs of switch contact-points, one pair on each of several boards, each pair normally in contact but open while the line is switched for conversation at their board and through an annunciator and a pair of contact-points normally which terminate the twosides of a loop which 1 contains a test receiving instrument, said plug being adapted to be inserted into one of the switches and when inserted to disconnect the contact-points of the switch which are normally in contact and connect them with the contact-pieces of the plug, and battery in the circuit established on testing, said test receiving instrument and battery being so I related that the instrument will sound when they are included in the simple normal circuit of theline but will not sound when the circuit is open at a pair of contact-points or the line is in circuit with another line or when the subscribers telephone is switched for useand the additional resistance is thereby included in the circuit, substantially as set forth.

4. In a telephone-exchange system, a telephone-line normally on closed circuit and passing successively through pairs of switch contact-points, one pair on each of several boards, each pair normally in contact but open while the line is switched for conversation at their board and through an annunci ator and a pair of contact-points normally closed but open while the annunciator indicates a call, in combination with switching devices at each board to disconnect said pair of contact-points at the board and switch the line for conversation, apparatus and switching devices at the subscribers station to include a greater resistance in the circuit of the line while his telephone is switched for use than when it isnot thus switched, and loop test-plugs, one at each board, each plug having two contact-pieces in whichterminate the two sides of a loop which contains a test receiving instrument and battery, each loop plug being adapted to be inserted into the switch at its board and when inserted to dis connect the said contact-points of the switch which are normally in contact and connect them with the contact-pieces of the plug, each test receiving instrument and its battery being so related that the instrument sounds when they are included in the norm-a1 closed circuit of any line but will not sound when thecircuit is open at any point or the line is in circuit with another line or the subscribers telephone is switched for use and the additional resistance is thereby included, substantially as set forth.

5. In a telephone-exchange system, multiple switchboards, telephone-lines normally on closed circuit, switches for said lines, one switch on each board for each line, each switch having a pair of contact-points normally in contact but open while the line is switched at their board, each line passing normally successively through the pairs of contact-points of its switches on the several boards and through an annunciator and a pair of contactpoints normally closed but open while the annunciator indicates a call, in combination with pairs of switch-plugs at each board, the contact-pieces of each pair being connected by a flexible-cord circuit, each of said plugs being adapted to be inserted into any switch at its board and when inserted to disconnect the pair of contact-points of the switch which pieces in which terminate the two sides of a.

loop containing a test receiving instrument and battery, said plugs being each adapted to be inserted into any switch at its board and when inserted to disconnect the contactpoints of the switch and connect them with the contact-pieces of the plug, and apparatus and switching devices at each subscribers station to switch a greater resistance into the circuit of his line while his telephone is switched for use than when it is not thus switched, each test receiving instrument and its battery being so related that the instrument sounds when they are included in the normal closed circuit of any line but will not sound when the circuit is open at any point or the line is in circuit with another line or the subscribers telephone is switched for use and the additional resistance is thereby included, substantially as set forth.

6. In a telephone-exchange system, multiple switchboards,telephone-lines normally on closed circuits, switches for said lines, one switch for each line on each board, each switch having a pair of contact-points normally in contact but open while the line is switched at their board, each line passing normally successively through the pairs of contact-points of its switches on the several boards and through an annunciator and a pair of contactpoints normally closed but open while the annunciator indicates a call, in combination with pairs of switch-plugs at each board, the two contact-pieces of each pair being connccted by a flexible-cord circuit, each of said plugs being adapted to be inserted into any switch at its board and when inserted to disconnect the pair of contact-points which are normally in contact and connect the contactpoint which is connected with the line with the contact-piece of the plug, apparatus and switching devices at each subscribers station to switch a greater resistance into the circuit of his line while his telephone is switched for use than when it is not thus switched, loop test-plugs, one at each board, each test-plug having two contact-pieces in which terminate the two sides of a loop which contains a test receiving instrument, each test-plug being adapted to be inserted into any of the switches at its board and when inserted to disconnect the contact-points of the switch and connect them with the contact-pieces of the plug, and battery in any test-circuit established on testing, each test receiving instrument and battery being so related and adjusted that the instrument sounds when they are included in the normal closed circuit of any line but will not sound when the circuit is open at any point or the line is in circuit with anotherline or the subscribers telephone is switched for use and the additional resistance is thereby included in the circuit, substantially as set forth.

7. In a telephone-exchange system, multiple switchboards, telephone-lines, each line grounded at its outer end, switches for said lines, one switch for each line on each board, each switch having a pair of contact-points normally in contact but open while the line is switched at theirboard, each line passing normally successively through the pairs of contact-points of its switches on the several boards and through an ann unciator and a pair of contact points normally closed but open while the annunciator indicates a call, and thence to ground, in combination with pairs of switch-plugs at each board, the contactpieces of each pair being connected by aflexible-cord circuit, each plug being adapted to be inserted into any switch at its board and when inserted to disconnect said pair of contact-points of the switch and connect the point which is connected with the line with the contact-piece of the plug, apparatus and switching devices at each subscribers station to switch a greater resistance into the circuit of his line while his telephone is switched for use than when it is not thus switched, and loop test-plugs, one at each board, each test-plug having two contactpieces in which terminate the two sides of a loop which contains a test receiving instrument and battery, each test plug being adapted to be inserted into any switch at its board and when inserted to disconnect the contact points of the switch and connect them with the contact-pieces of the plugs, each instrument and its battery being so related and adjusted that when they are included in the normal closed circuit of any line the instrument will sound but will not sound if the circuit is open at any point or the line is in circuit with another line or the subscribers telephone is switched for use and the additional resistance is thereby included in the line, substantially as set forth. In witness whereof I hereunto subscribe my name this 13th day of December, 1889.

MILO G. KELLOGG. Witnesses:

EMIL ABENHEIM, MARGARETHA RIEHL. 

